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Texas Emergency Management ONLINE 2016 Vol. 63 No. 9

Fall & Winter Wildfire Potential Outlook

Looking ahead to the fall of 2016 and winter of 2017, there are a couple of concerns that could promote increased wildfire activity. First is the abundant growth of grasses across the state brought on by the above normal precipitation levels of late spring and early summer. (See graphic below) The second is the forecasted return of La Niña conditions which could be in place by this fall.

Late spring/early summer precipitation is very important to the expectations and potential for a summer, fall, or winter fire season. It sets the table by either restricting or enhancing the amount of grass growth across the landscape. With the above normal precipitation levels experienced this year, just like last year, it has produced a bumper growth of grass. This is especially the case in the areas shaded in greens and blues in the above map. These areas cover some of the states more fire-prone areas. Eventually these grasses will cure and become a potential fuel for a wildfire.

Another indicator that could signal the potential of a fall or winter fire season is the ENSO (El Niño Southern Oscillation) phase. ENSO phase reflects the departure from normal of sea surface temperatures in Pacific Ocean along the equator west of South America. A cooling of these waters is referred to as the La Niña phase, and the warming of them as El Niño. Neutral would be whenever neither is present. NOAA has 50 plus years of data on the impacts of each ENSO phase on US weather. For Texas, above normal moisture has occurred during the late fall through early spring months most of the time when an El Niño is present and below normal moisture with La Niña. ENSO phase has been a fairly reliable indicator of expected moisture levels for the fall through spring months.

According to the graphic below, produced by NOAA's Climate Prediction Center on July 14, 2016, there is a 55 to 60 percent chance of La Niña conditions being present this fall and winter, then fade by early spring.

Even though this is a forecast, it does indicate there is a decent chance of La Niña occurring sometime this fall and into the winter. With that being the case, the Climate Prediction Center is forecasting above normal temperatures and below normal precipitation for Texas during this period. (See the following graphics)

Temperature

October – December Temperature             December – February Temperature

Flood Escort

October – December Precipitation             December – February Precipitation


The emergence of La Niña conditions this fall could signal the onset of a drier and warmer than normal climate for the state from October through next March.  Conditions like these in the past have combined to produce some of our most active fall, winter, and spring fire seasons.  Examples include the fall – spring periods of: 2005-2006, 2007-2008, and 2010-2011.  In each of these cases, the late spring-early summer rains produced heavy grass growth.  Once these grasses cured, they served as ready fuel beds for wildfires.  This year, so far, appears to be following a similar scenario.  Wildfires burning under the conditions expected this fall and winter can be dangerous and threaten the property and safety of Texans when and where they occur.  Caution is advised to stay alert to the evolving situation as the fall and winter months move closer.

The threats for increased wildfire potential this fall and winter include:

  1. Increased grass fuel loading across the state
  2. The emergence of La Niña which is expected to produce:
    1. Above normal temperatures
    2. Below normal moisture

Contributor:
Tom Spencer
Texas A&M Forest Service
College Station, Texas 77845


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